1. Field of the Invention
The invention is generally directed to interferometer Fourier transform spectrometers and, more particularly, to a high speed interferometer Fourier transform spectrometer which performs the Fourier transform in parallel, in analog form, using a weighted matrix multiplication.
2. Description of the Related Art
One type of known spectrometer is comprised of an input slit, a dispersion means which is typically a prism or a grating, and a detecting means to measure the magnitude of the spectral components. The input slit is required to avoid overlapping the spectra from different parts of the field of view. A drawback to this spectrometer is that it requires a very narrow slit for high resolution, which reduces the optical throughput of the system.
A spectrometer which does not require dispersing the spectrum, and thus makes available a larger flux of light, is an interferometer spectrometer. Instead of dispersing the spectrum, an interferometer spectrometer sorts the wavelengths by creating an interference pattern of the incoming light (an interferogram) and converting this pattern to a spectral distribution through use of a Fourier transform. The conventional Fourier transform spectrometers, as described in Takayuki Okamoto, Satoshi Kawata, & Shigeo Minami, "Fourier transform with a self-scanning photodiode array," Applied Optics, Vol. 23, No. 2, Jan. 15, 1984, use linear photodiode detector arrays and analog-to-digital converters, with the Fourier transform calculated in the digital domain. This architecture places very wide dynamic range requirements on the self scanned photodiode array, high precision and high speed requirements on the analog-to-digital converters, and very high speed computational demands for the Fourier transformation on the spectrometer.